The simian retroviruses simian T-lymphotropic virus 1 (STLV 1), simian immunodificiency virus (SIV), and type D retrovirus are important animal models for the study of human immunodificiency and also pose a threat to the health of captive domestic breeding colonies. Herpesvirus simiae (HBV) is a proven hazard to animal care workers and laboratory personnel. The New England Regional Primate Research Center proposes to establish a specific-pathogen-free (SPF) breeding colony of 225 rhesus monkeys to provide uninfected experimental subjects and to improve colony health. The breeding colony will be self-sustaining and will provide approximately 25 SPF rhesus monkeys for the ongoing and federally funded research programs at the Center. Uninfected animals will be identified using proven serologic and virus isolation techniques. SPF animals will be group housed in a dedicated modern concrete block building. The SPF status of the colony will be ensured through periodic serologic surveillance. The genetic diversity of the breeding colony will be maximized by tracking of individual animal pedigrees and avoiding inbreeding when forming breeding groups.